It's a common complaint among Botox patients and those who interact with them: The wrinkle-zapping injection dulls a person's ability to convey emotion through facial expressions. Sure, this can be bad news for interpersonal relationships — but it may actually be an asset for battling depression, according to a new study. Here's what you should know:

How was this study conducted?Researchers selected 30 participants suffering from major depression. Half were given five injections of Botox between and just above the eyebrows while the other half were given placebo injections in the same places. After six weeks, health care professionals ranked the patients' depressive symptoms — including sullen mood, insomnia, and weight loss — and reported back to researchers.

What did researchers find?Patients who were injected with the placebo had a 9 percent reduction in depressive symptoms, while patients injected with Botox had a 47 percent decrease in symptoms. Such mood elevations held steady throughout the rest of the 16-week study period for both groups.

Why is this?We already know that muscles in your face communicate your emotions to other people. But this study suggests that these facial muscles are also instrumental in regulating your own mood. How? The study's author, M. Axel Wollmer, a psychiatrist from Switzerland's University of Basel, posits that Botox helps block negative feedback "from the facial musculature to the brain, which may be involved in the development and maintenance of negative emotions." Essentially, your facial muscles might not just tell other people how you feel — they might tell your brain how you feel, too. And because Botox relaxes those muscles, it may prevent your face from telling your brain that you're blue.